Have my neighbors started a drug lab?

I live on a quiet street in a nice neighborhood - but the occupant of the house next door recently got a shady looking roommate. Now all the windows are covered in blankets and towels. Where there used to be no visitors, there is now a constant parade, bikers, skanky women, guys in monster trucks - always travelling in pairs. They have a new rottwieller they never walk, and security lights in the back. The original guy now has a Harley even though he doesn't appear to make much money. There are often 5 or more cars parked out front, yet there is never anyone in the backyard nor does any noise come from the house. The people stay inside the tiny house for many, many hours. There seemed to be a funny, sweet, chemical smell in the yard earlier this evening. What is going on with these people? (And yes I do have a life, a good one actually. I don't want it diminished in any way by some dirtbag neighbors.)